Voltage regulator



J1me 1949. G. B. STEINCROSS 2,474,287

VOLTAGE REGULATOR Filed Sept. 4, 1945 lNVENTOR GERALD B. 8 TE INCROSS RO YMkW ATTORNEY Patented June 28, 1949 UNITED STATES PATENT OFFICE VOLTAGE REGULATOR Gerald B. Steincross, Long Beach, Calif.

Application September 4, 1945, Serial No. 614,327

2- Claims. (01. 322-18) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) This invention relates to voltage regulators and more particularly to a device for automatically constraining output voltage surges of motor generators.

Electrical devices energized by motor generators are occasionally subjected to violent voltage surges of sufiicient intensity to cause material damage when the generator is loaded. This has been particularly true where alternators having a compensating field connected in series with the armature of a driving motor have been employed and the recommended operating power factor of the alternator is exceeded. With the application of a load to such an alternator, a surge of current occurs in the compensating field which results in an abnormally high voltage output.

It has been found that the voltage surge can be reduced to a safe value by providing a resistance in parallel with the compensating field as a shunt circuit. While such a resistance makes the output of the alternator safe, it restricts the output voltage and renders the alternator inefficient during constant load operations.

The principal object of my invention is, therefore, to provide improved means for overcoming voltage surge in the output of a motor driven alternator.

Further objects of my invention are to provide a means for regulating the voltage output of alternators so as not to interfere with the electrical output thereof under conditions of constant load; to provide a device for shunting the compensating field of the alternator while a load is being suddenly applied; to provide a device for interrupting the shunt circuit when the danger of voltage surge has passed; to provide improved elements and arrangements thereof in a compact electrical device of the character described; and to accomplish the noted objects in a facile, economical, and eflicient manner.

In accomplishing these and other objects of the present invention, I have provided improved details in the structure of the electrical device the preferred form of which is illustrated in the accompanying drawing, wherein the figure is a diagrammatic illustration of the electrical device embodying my invention.

Referring more in detail to the drawing:

It will be noted, generally, that a motor I and an alternator 2 mechanically driven by the motor are shown. Certain conventional elements, presently more fully described, are shown Within the motor I and the alternator 2 to assist 2 in describing the operation of the present invention.

Electrical energy is supplied to the motor I and the generator 2 through a motor field lead terminal 3, a motor line lead terminal 4, and an alternator armature terminal 5; the motor field lead terminal and alternator armature terminal being of the same polarity.

6 designates a speed regulator for the motor and may comprise a potentiometer as shown or a variable resistance. Connected in parallel to the regulator to provide in cooperation therewith a wider range of speed regulation than achieved b the speed regulator acting alone is a by-pass switch I.

Connected in series with the parallel circuit consisting of the regulator 6 and variable resistance I, is a motor shunt field 8 completing an electrical circuit between terminals 3 and 4.

A motor commutating field 9 in series with a motor armature II) is indicated within the motor I also communicating with the terminal 4.

Within the alternator 2, II designates a potentiometer used to control the voltage output of the alternator, I2 the shunt field of the alternator, connected in series with the potentiometer II, and I3 the alternator compounding field, connected in series with the motor armature I0.

Alternator slip rings I4 and output terminals I5 and I6 are shown as provided in conventional alternators.

The field coils of the alternator are energized by connecting the potentiometer II of the alternator to the terminal 4 and the alternator compounding field I3 to the motor armature II].

In the use of the motor I and the alternator 2 the placing of a sudden load on the alternator imposes an increased mechanical load on the motor. The increased mechanical load on the motor I results in an increased flow of electrical current through the armature III and through the compounding field I3 of the alternator resulting in an increased voltage across the terminals I 5 and I6. The load placed on the alternator I may increase the power factor thereof beyond the recommended operating value. In such instances, the resulting voltage surge is frequently of sufiicient violence to injure the electrical equipment being energized thereby.

The following means are provided to accomplish the noted objects:

To prevent a surge of current from passing through the compounding field I3 of the alternator, a compounding field shunt circuit I l is provided. The shunt circuit I1 is connected to 3 the electrical circuit of the alternator 2 in parallel with the compounding field l3 as at [8 and IS.

The shunt circuit l'l comprises a compounding field shunt resistor 20 and a shunt circuit relay 2| connected in series. The shunt resistor 20 is properly matched with the alternator compounding field l3 to piovider-wby-pass path of the desired resistance. The shunt circuitrelayflfl is closed only when it is desired to utilize the shunt circuit l1 and is commonly known as a maker. circuit relay.

The electrical equipment being energized by the alternator 12 requires protectiiom against :.excessive voltage surges only whenthe output voltage of the alternator is suffiCiently-highthatasummation of the output voltage and asvoltage surge is of dangerous magnitude.

With this in mind a shunt trelay operating circuit 22 is provided to openvand -to close-the shunt relay 2|. an operating. circuit :22 .iconsists ,of: lar relay; oper-, ating coil 23 and a time delay relay 24, here-: inafter described, connected-miseri s bntweemthe alternator terminals; l5-.:and;; l6; Theaactuating element operating coil 23 :is *of; such; rating; as to close the shunt relayi 2 l only-when arvoltage approaching or surpassing the normal; operating voltage of the alternatorflds impressedronthe operating-circuit-122-:-. The;;time delayrelay is opened only, to. interrupt the shunt: relay operating circuit 221:and:is commonly-known:,as a break circuit time delayerelay The danger of excessive voltage output; from the alternator-:2 :exists for-wonlyaa briefperiod after the sudden loading of the alternator.:

Further, if the a shunt. :circuit a l I is maintained during lconstantqload operating :conditions; cur-: rent needed-to excite the:;compounding field-is permitted to by-pass. it andlthevoltage output "of the alternator is.;reduced=.i, It'thus;.is:.-ohvious that it is advantageous tointerrupt the shuntcircuit l1 after thebrief danger. periodhaspassed-t To this. end; a .time delay -..relay. roperating. circuit '25 is furnished;sfor:.'operating:.the relays. The time delay relay: operating cirouit 125 Hcomprises an actuating-element; such asan operating coil 26 in the time delay relay 24connected -.in series with a current-(relay 2'l across the output terminals 1 and I 6 of= the alternator '2 =as '-at 28 and '29. The time:delay relay=-26 is or a type that opens a brief period after having'its "actuating element 26 energized The current-relayl'l, commonly referred to as a-makefzcir'cuit 'type, is normally open closing only-when itisdesired to complete the time relay circuit-25.1

The current relay 2! is= preferably adj ustable to permit therelay to -be-set to -open and to close at the amperagesdesired.- In order-to' obtain accurate adjustment with ail-economical relay a current relay operating-ondow amperages -is-used.

Referring again-to the motor I =an'd thealternator 2, when anoperating -loadzis put across the terminals I5 and l6-the alternator putsa greater mechanical load on the'motor l. The increased demand forpower on-the-shaftof-the motor causes a greaterfiowof electrical-current between the motor armature I'O and the compounding field l3 of the alternaton; This--fact is utilized in i controlling the current relay 21 The current relay '21 hasanactuating element such as an operating coil- 3ll' thatconnected by a current relayopera'tingcircuit 3t -in-series with the armature -IB and the compounding field l3 to open'andto close thecurrentyrelay 121 in response to current fiuctua-tions'.

The actuating element such as 1035. The selector switch is used to by-pass the To permit the use of an economical, low amperage current relay at 21, to provide a greater range of adjustment of the relay, and to keep its operating current within safe bounds when either a or 230 volt power supply is employed to energize the motor I and the alternator 2, a shunt resistance circuit--32 is arranged to by-pass the current relay-21. The shunt circuit 32 includes a pair of resistors 33 and 34 and a selector switch operating. coil 30 by providing a shunt circuit through either the resistor 33 or 34 or through both :ot themarranged in parallel.

As an additional protective measure, an electric fuse element -36is provided in series with the operating; coil 30.

Operation The operationuof the voltage regulator constructed as described is as follows:

The current relay 2'l .is adjusted toibe opened and closedas desired in responser-to-the current flowing throughthecoil 30, For-example, it

may be found practical to set the relay 21 to close at approximately 3.5 ampereszand'to-open at approximately 2.5 amperes.- switch 35is then adjusted-until the current relay 21 carries current in-excess vofv3.5 amps. during voltage surge conditions but: carries current of less than :25 amps. duringgnormalopperatiorn When the motor I and the alternator] are at rest the compounding fieldshuntl relay *2! and the current relay 21' areopen, interrupting the circuits [1 and:=25, and-the time delayrelay 24 is in a closed position; completingthecompounding fieldv relay operatingcircuitfl. Thecurrent operating circuit 3| has no "interrupting means andistherefore always in a closed condition.

When the source of-zpower is connected to the motor I andthealternatorZ at terminals3, 4;

andi, themotor and alternatoragraduallyacceler-ate from a standstill position to. a: [normal running speed. The fields ofthealternator2 being excited, an, .increasing voltage (is built up across the terminals. 15 and lfitinresponsetoalternator acceleration. The shunt relay operating circuit 22 bein connected betweentheterminalsciii'and l6 hasimpressed .upon'it .a gradually increasing voltage in response totheaccoloration and the alternator.

Just before the normal output voltageofthe alternatorZ'is reached, sufficient voltageis impressed on the shunt relay operatingcircuit 22 to close the shunt relay'2 I and complete the shunt circuit I l Socompletedjtheshunt circuit ll provides a by-pass path parallel to the-compounding field I3 of the alternator. As long as the-alternator 2 "continuesrto develop a sufiicient output voltage and as long as thetimeldelay-relay 24 remains closed, the shunt relay operating circuit 22 maintains the relay 2! in closed position Thus at all times when the motor l and alternator 2 are rotating at a normal speed and there is no load imposed on the alternator; the compounding field shunt circuit I! isready to by-pass the compounding field l'3 with any; excessive. current caused by the sudden impositionof a'load. The shunt circuit [1 continuestobir-passthe compounding field .l3 so-long-as thecurrent :in the compounding field circuit continues to remain below the predetermined-magnitude at which the current relay 21 will beactuated- This feature makes this apparatus useful, for example, in sup- The selectorplying certain types of electronic equipment which, on standby condition, draw a low load consisting only of sufiicient current to keep the electronic tube filaments heated and'ready for instant operation, and which, on operate condition draw perhaps the full rated load of the generator. When used with such electronic equipment, this apparatus keeps the compounding field shunted during standby condition and is prepared to protect the electronic equipment from transient surge voltages occasioned by the current surge resulting from the switchover from standby (low load) to operate (full load).

Upon the sudden placing of a load on the alternator 2, such as by switching over attached electronic equipment from standby to operate whereby the electrical drain on the alternator is increased from low load to full load, a greater machanical load is put on the shaft of the motor .The increased shaft load on the motor slows the motor and causes a surge of current to fiow through the motor armature I and the alternator compounding field 13 by way of the current relay operating circuit 3| and the shunt resistance 32. bilizes at an increased substantially constant magnitude, for example, the full load value for the attached electronic equipment, which causes a constant flow of current in the circuit 3| that exceeds the predetermined value required for energization of the current relay 21. The current relay 21, bein previously set to operate upon such an increased magnitude of current, closes and completes the time delay relay operating circuit 25.

The compounding field |3 escapes the surge of current by said current surge being shunted through the compounding field shunt circuit l1, this circuit having already been closed as the normal output voltage of the alternator was approached.

With the closing of the current relay 21, the time delay relay operating circuit 25 and the time delay relay actuating element 26 therein are energized. The time delay relay 24 is adjusted to delay a brief period after the energizing of the actuating element 26 before opening, thus insurin that the compounding field I3 is shunted during the transient period, such as when the attached electronic equipment is switched over from low load to full load, in order to make certain that the generated voltage of the alternator is kept within proper limits which might otherwise be exceeded by virtue of the increased field flux in the alternator caused by a transient current surge in the compounding field coils.

After a sufficient period of time has passed for the surge of current to by-pass the compounding fieid It, the time delay relay 24 opens, breaking the shunt relay operating circuit 22, which in turn opens the shunt relay 2| and interrupts the compounding field shunt circuit ll. At this point the danger from current surge has passed, the shunt circuit I! is no longer required as a current surge by-pass, and it is thus interrupted so that it in no way interferes with the loaded operation of the alternator.

In a similar manner when the load is taken off of the alternator at l5 and IS, the current flowing through the current relay operating circuit and shunt resistance 32 suddenly drops. The current relay 2'! is opened by the drop in the current passing through its operating coil 30. When the current relas 2! opens, the time delay relay operating circuit 25 closes, the time delay relay 24 This current finally stacloses, the shunt relay operating circuit 22 closes, the shunt relay 2| in turn closes and the compounding field shunt circuit l1 again is ready to protect the compounding field l3 from any current surge that may again occur. The shunt circuit remains in such protective arrangement until either the alternator is again loaded or the motor and generator are turned off.

When the motor and the generator are turned off the current flowing through the shunt relay operating circuit ll drops to a point below'which it can maintain the shunt relay 2| in a closed position and the shunt relay opens, interrupting the compounding field shunt circuit. Thus, again while there is no danger from a sudden current surge between the armature l0 and the alternator compounding field l3, the compounding field shunt circuit is disengaged and will provide no dissipation of energy by icy-passing the compounding field until the voltage again approaches normal operation and protective shunting is again required.

While I have shown but one embodiment of my invention, it is susceptible to modification without departing from the spirit of the invention. I do not wish, therefore, to be limited by the disclosures set forth, but only by the scope of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. In an apparatus of the character described including a motor generator set, the motor of which is provided with a series field and the genorator of which is provided with a compounding field; a shunt circuit across said compounding field including a shunt resistor and a shunt relay connected in series, the shunt relay being set to maintain said shunt circuit closed in response to approximately normal voltage of said generator; an operating circuit for said shunt relay including a time delay relay connected in series with the actuating element of said shunt relay between the output terminals of said generator, the time delay relay being adjusted to open the shunt relay operating circuit after the lapse of a predetermined time period after the energization of said time delay relay; an operating circuit for said time delay relay comprising a current relay connected in series with the actuating element of the time delay relay across the output terminals of said generator, said current relay being adjusted to close said time delay relay operating circuit when the current flowing through the actuating element of said current relay exceeds a predetermined magnitude; and an operating circuit for said current relay connecting the actuating element thereof in series with the armature and series field of said motor and the compounding field of said generator; whereby said shunt circuit is opened a predetermined time aiter the load on said generator exceeds a predetermined magnitude.

2. In an apparatus of the character described including a motor generator set, the motor of which is provided with a series field and the genorator of which is provided with a compounding field, said series field and said compounding field being connected in series; a shunt circuit across said compounding field to limit the voltage output of said generator upon sudden increase of load, as during the change from low load to full delay relay arrangement controlled by the curroad condition; and means comprising a time ,flEFmENCES CITED rent in the circuit of said compounding field for The following l es a of record in the opening said .shunt circuit a. predetermined time file this: pat nt:

after the current in'said compounding field oir- 5 UNITEDSTATESPATENTS cult has exceeded a predetermined magnitude;

whereby :full compounding field current flows Number Name Date through the compounding field after'said gen- 1,116,430 Jackson 1914 erator has reached its steady state full load 2,009,103 B37185 July 23, 1935 condition. 10

(HERALD B. STEINCROSS. 

